Corona reducing armor rods



y 1965 s. N. SCHLEIN 3,193,616

CORONA REDUCING ARMOR RODS Filed July 12, 1963 2 Sheets-Sheet 1 Fig.3

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' CORONA REDUCING ARMOR RODS Filed July 12, 1963 2 Sheets-Sheet 2INVENTOR. sfiYflouk. N. SCHLEM kUW N ATToRNeY United States Patent3,193,616 CORONA REDUCING ARMOR RODS Seymour N. Schlein, UniversityHeights, Ohio, asslgnor to The Runner Manufacturing Company, a Divisionof Tcxtron, Inc., Cleveland, Ohio, a corporation of Rhode Island FiledJuly 12, 1963, Ser. No. 294,609 5 Claims. (Cl. 174-127) This inventionrelates to improvements in armoring for high voltage conductors and moreparticularly to a means for reducing corona discharge and damage fromthe armoring to the conductor.

As is well known, it has become common practice to provide devices,known as armor rods which are applied to conductors for the purpose ofreinforcement. Such devices are'shown and described in Patents Nos.2,587,521 and 3,087,008.

When such devices are used in conjunction with high voltage transmissionlines, a problem arises in that at the sharp ends of such rods there isa concentration of the electrical field which causes an ionization ofthe air in the immediate vicinity and a resultant brush discharge,commonly known as corona discharge. Corona discharge represents a lossof power, the creation of ozone in the vicinity of the conductor and aresultant deterioration of the conductor, and causes static whichinterferes with communications.

Various expedients have been suggested for the elimination of thiscorona, one of which is disclosed in my copending application Serial No.346,670, filed December 20, 1962, and contemplates the provision of aring on the end of one of the rods which extends outward in spacedrelation surrounding the line. Still other means contemplates the use ofattachments which are secured to the end of the rods to provide anincreased distribution of the field outwardly of the line.

. All of these devices increase the cost of the installation.

Although some of the devices, such as shown in Patent No. 3,087,008, donot materially increase the cost of the installation, they have thedisadvantage that at the extreme end of the rod, where the outer surfacemerges with the inner diameter of the helix, there is provided a sharpknife edge or point. This knife edge has the disadvantage that greatcare must be observed during the installation and removal of the rods,or the point will cause the outer wires of the line to which it isattached to be nicked by the points. This nicking defeats the purpose ofshaping the ends because the nicking provides sharp spicules which causethe generation of corona.

In addition, the sharp points bear against the outer surface of the lineand the vibration of the line causes a working of the points on the linewhich frets the line and in time causes a wear or sharpening of thepoints which leaves a sharp knife edge on the extremities that is spacedfrom the line and increases instead of decreases the corona.

Furthermore the points which are on the ends of the rods are apt tobecome damaged during shipment as well as damaged during installation,due to the fact that they are small, needle-like and subsequentlysomewhat fragile. Even though the rods are normally made of a hard drawnresilient material, they can be bent very easily and thus are worse thanthe ordinary rounded or ball end rods.

In the larger of the transmission lines, where the lines carry very highvoltages, such'rods may have a rod diameter from A to /2" and sometimeseven larger. In the interest of reducing the weight and in economizingin material it is possible to make such rods of a tubular stock. Withsuch tubular stock it would be even more difficult to provide an endformation which has the desired configuration. Normally the rods aremade of solid stock.

Further such ends, when made of tubular stock, if damaged, provideleakers into which moisture may enter, eventually providing a sufficientaccumulation that in cold weather it can freeze and cause the rods tosplit. This would leave sharp edges, both at the point where themoisture enters and the place where the rod splits.

The present invention contemplates the provision of an armor rod whichmay be put to all the uses normally made of armor rods and wherein theend is provided with an improved formation which greatly reduces thedefects of the prior art delineated above.

Still otheradvantages of the invention and the invention itself willbecome more apparent from the following description of an embodimentthereof, which description is illustrated by the accompanying drawingsand forms a part of this specification.

In the drawings:

FIG. 1 is a fragmentary elevational view of a set of armor rods, showingthe manner of their application to a line which is shown in dottedlines; 7

FIG. 2 is a view taken from the line 2-2 of FIG. 1, with the position ofthe line shown as a solid section;

FIG. 3 is an enlarged end view of a single rod;

FIG. 4 is an enlarged fragmentary view of the end portion of a rod takenfrom the outside; and

. FIGS. 5 and 6 are similar views taken at and from that of FIG. 4.

In the drawings like parts have been designated by like referencecharacters.

Briefly, my invention contemplates an armor rod, solid or hollow, whichis formed of hard, resilient material, in the form of an open helixcapable of being applied to a line from its side without permanentdeformation of the rod. Preferably the helix is formed with an insidediameter slightly less than that of the line and a pitch that isslightly shorter than the pitch of the line, although it may be longer.The end ofthe rod is provided with an outer portion which curves towardthe inner diameter of the helix and an inner surface which curvesoutwardly toward the outer diameter of the helix, the two surfacesmeeting in a spatulateend zone which is curved transversely to the axisof the helix.

More specifically, as shown in FIG. 1, a plurality of rods 10 areprovided, being shown in place on a conductor 11. The rods preferablyare designed to provide a complete sheath surrounding the conductor,although commercially it has been found that good results are obtainedeven if the sheath is not complete. A slight gap is desirable because inthis instance it can be assured that the rods engage with the conductortightly which they could not do if the rods were large enough so thattheir combined diameters at their point of tangency was greater than thecircle at that point around the conductor.

As can be seen from FIGS. 1 to 3, the extremities of the rods areprovided with spatulate ends 12. These ends, as viewed from the outerside of the helix, may be curved on a radius equal to the diameter ofthe rod, straight, or, flattened in a Zone on opposite sides of thecenter of the rod with a curvature toward the ends, the last being illustrated in FIG. 1.

As best shown in FIG. 2, it is preferred that, as viewed from the ends,these extremities 12 be slightly curved so that these surfaces on theends when installed on a line have a curvature on a radius equal to thatof the inside of the helix plus the distance from the inner diameter ofthe helix to the center of the surface 12. When so made, they would alllie in a circle having slight interruptions between the rods, as viewedin FIG. 1. If the ends were straight, as viewed from the outside of thehelix and curved as viewed from the ends, there would be no interruptionand they would form a continuous ring on the end. In addition, if theywhere straight as viewed from the end, they could form a polygon.

Of particular importance is the formation of the outer and innersurfaces at the ends, which surfaces extend from the inner and outerperiphery of the rod to the end zone 12.

As best illustrated in FIGS. 4 and 5, the outer surface starts at apoint 14a and gradually curves downward to the end 12. This curvatureshould preferably be on a radius at least equal to the radius definingthe outer diameter of the helix, although it does not necessarily haveto be a true arc. Crosswise of the surface 14 it starts as a curve 14a,which is defined by the radius of the rod, and gradually flattens towardthe end. As stated, the extremity may be that of an arc of a circle, asshown in FIG. 2, or straight.

It is preferred that the surface 14, where it terminates at the end 12,be outward from the inner surface of the rod a distance substantially10% to 50% of the diameter of the rod.

The inner surface of the rod curves outwardly at the endto the zone 12,as best shown at 16 in FIGS. and 6. To this end, the inner curvedsurface may start in a narrow zone 16a and curve outwardly and laterallyas shown at 16b, and finally curving inwardly at the end and mergingwith the zone 12. As viewed from the side, the outward curvature 16,FIG. 5, may be on a radius approximately the same as the diameter of therod and preferably not less than the radius of the rod. The ends may beformed by a suitable swaging operation in properly formed dies. Shouldthere be any flash metal on the end, it may then be ground off toprovide the zone 12. Preferably the'zone 12 is not a clearly definedzone but is a zone the top and bottom of which merges smoothly with thesurfaces 14 and 16.

It will thus be seen that the inner end surface 16 provides a roundedend which cannot scratch or nick the line during application.Furthermore after application the line may move or work longitudinallyrelative to the rods, without the rods fretting the line or the rodswearing at the ends to a sharp edge.

The curvature of the portion 14 is such that it causes a reduction ofthe electrostatic field. It is believed that this surface with thesurface of the conductor act together to prevent the end zone 12 frombeing a source of corona.

Having thus described the invention in some embodiments thereof, I amaware that numerous and extensive departures may be made therefromwithout departing from the spirit or scope of the invention as definedby the appended claims.

I claim:

1. For use in combination with a high voltage line, a corona reducingarmor rod comprising a hard drawn resilient member in the form of anopen helix having an inner diameter less than the diameter of the line,the improvement which comprises at least an end of said rod shaped toprovide an outer portion starting spaced from the end of the rod, whichcurves toward the inner diameter of the helix and a surface on the innerside of the rod which curves outwardly toward the outer diameter of thehelix, the two described surfaces meeting to form a spatulate end zonewhich is curved transversely to the axis of the helix.

2. A device as described in claim 1, in combination with the linewherein the ends extend in a circumferential zone spaced from theperiphery of the line.

3. A device as described in claim 1, in combination with the linewherein said ends are curved to conform to a circumferential lineextending around and spaced from the line.

4. For use in combination with a high voltage line conductor, apreformed helical member of resilient conducting material having aninside diameter slightly less than the conductor and an open pitch suchthat it may be applied to the conductor without permanent deformation,

said helical member having at least one end formed to cause greater areadistribution of the electrical potential, to prevent corona, comprisinga portion at the end extending from the inner diameter of the helix awayfrom the conductor for a distance between 10% and 50% of the diametricalcross section taken through said member, the outer surface of said endcurving downward toward the helical axis for a distance between and 50%of the diametrical cross section of said member to meet said firstcurved surfaces, said curved surfaces forming an end which is curved ona radius at least equal to a radius of said member and extending on ageometrical line substantially perpendicular to a diametrical line drawnthrough said helix.

5. A device as described in claim 4, in combination with the linewherein said high voltage line is provided with a substantially completesheath formed by a plurality of preformed helical members and said endsare disposed in the plane of a ring surrounding said high voltage linewith the inner extremities being curved away from the high voltage lineand the outer extremities curving toward said high voltage line, thecurvature of the outer extremities being on a radius at least equal tothe radiusof the high voltage line and the curvature of the innerextremities being on a radius less than that of the high voltage line.

References Cited by the Examiner UNITED STATES PATENTS 2/52 Peterson174--136 X 4/63 Ruhlman 174-127 OTHER REFERENCES JOHN F. BURNS, PrimaryExaminer.

DARRELL L. CLAY, Examiner.

1. FOR USE IN COMBINATION WITH A HIGH VOLTAGE LINE, A CORONA REDUCINGARMOR ROD COMPRISING A HARD DRAWN RESILIENT MEMBER IN THE FORM OF ANOPEN HELIX HAVING AN INNER DIAMETER LESS THAN THE DIAMETER OF THE LINE,THE IMPROVEMENT WHICH COMPRISES AT LEAST ON END OF SAID ROD SHAPED TOPROVIDE AN OUTER PORTION STARTING SPACED FROM THE END OF THE ROD, WHICHCURVES TOWARD THE INNER DIAMETER OF THE HELIX AND A SURFACE ON THE INNERSIDE OF THE ROD WHICH CURVES OUTWARDLY TOWARD THE OUTER DIAMETER OF THEHELIX, THE TWO DESCRIBED SURFACES MEETING TO FORM A SPATULATE END ZONEWHICH IS CURVED TRANSVERSELY TO THE AXIS OF THE HELIX.